A photonic chip and an electrical chip can be wire bonded to a common substrate. However, using wire bonding to connect a photonic chip and an electrical chip to a common substrate has several drawbacks. For example, using wire bonding to connect the photonic chip and the electrical chip to a common substrate requires the use of external ceramics or BGA substrates with vertical interconnect accesses (vias), which is not desired for achieving dense integration with other application-specific integrated circuits (ASICs). Also, using wire bonding to connect the photonic chip and the electrical chip to a common substrate requires that the I/O interfaces are arranged on the top surface of the photonic chip, which limits the number of I/O interfaces.